FIELDABLE NUCLEAR MATERIAL IDENTIFICATION SYSTEM
Daniel E. Archer, Charles L. Britton, Jr., Robert J. Carter, Randal F. Lind,
John T. Mihalczo, James A. Mullens, James E. Radle, Michael C. Wright
Oak Ridge National Laboratory
P.O. Box 2008, Oak Ridge, TN 37831
ABSTRACT
The Fieldable Nuclear Material Identification System (FNMIS), funded by the NA-241 Office of
Dismantlement and Transparency, provides information to determine the material attributes and
identity of heavily shielded nuclear objects. This information will provide future treaty participants
with verifiable information required by the treaty regime. The neutron interrogation technology
uses a combination of information from induced fission neutron radiation and transmitted neutron
imaging information to provide high confidence that the shielded item is consistent with the host’s
declaration. The combination of material identification information and the shape and configuration
of the item are very difficult to spoof. When used at various points in the warhead dismantlement
sequence, the information complimented by tags and seals can be used to track subassembly and
piece part information as the disassembly occurs. The neutron transmission imaging has been
developed during the last seven years and the signature analysis over the last several decades. The
FNMIS is the culmination of the effort to put the technology in a usable configuration for potential
treaty verification purposes.
INTRODUCTION
The Nuclear Material Identification System (NMIS) is an active and passive interrogation system
developed and refined at the Oak Ridge National Laboratory (ORNL) over the past 20 years.1,2 The
purpose of the system is to characterize both the fissile and nonfissile material in a containerized
target that may have some of the materials of interest shielded from typical radiological
measurements. The system can be used in the passive mode to analyze radiological emissions from
nuclear materials, or with the addition of neutron and/or gamma interrogation, it can be used in the
active mode to analyze radiological emissions caused by the interaction of the source neutrons or
gamma rays with the target material. Both provide a nuclear reaction signature of the target that can
be used for attribute determination and template matching to similar targets. The interrogation
source is an associated particle D-T (deuterium-tritium) neutron generator. In addition to the NMIS
signature capabilities, imaging capabilities have also been developed and added to NMIS over the
past seven years.3,4 The use of imaging with attribute determination capabilities can provide a high
confidence level that the special nuclear materials (SNM) and other materials in the target are
consistent with what has been declared by the host country.
Radiographic and tomographic imaging is accomplished through the detection of time and direction
stamped neutron emissions passing through the interrogated target in conjunction with an array of
1 x 1 x 4-inch plastic detectors on the opposite side of the target. During the image scanning
process, the attenuation of the neutrons is measured versus the anticipated path of the neutron
through the target for any elevation desired. For axial symmetric targets, this information can be
obtained from a single scan of the target. For nonsymmetrical targets, multiple scans must be
completed from various angles relative to the target to provide the data necessary for the
1
tomographic image reconstruction. Upon completion of the scan and determination of the
attenuation through the various parts of the target, software can analyze the data and provide a 3D
image reconstruction of the target.
A D-T neutron generator is the interrogation source most often used for imaging. The high energy,
time and direction tagged neutrons provide high penetration of the target, even through dense
materials. However, there are occasions for low attenuating objects where a 252Cf source is
desirable.5 Its neutrons and gamma rays are time tagged but not directionally stamped. The gamma
ray attenuation can provide more detailed images, and the fission spectrum neutrons can provide
more image contrast for the low-density materials in the target.
While NMIS has been developed and refined over the past 20 years, it should be noted that it has
also been used in several practical applications
such as accountability applications in a
production mode. This was accomplished by
utilizing the NMIS signature capabilities to
inspect the shipment and receipt of containers
to determine if the declared material was
actually present in the container or within the
target.6 It was also used to determine an
estimated quantity of material in special
situations due to the discovery of unknown
quantities or material types discovered in
Figure 1. Image of material in processing pipe.
containers or processing equipment (Fig. 1.).7
The usefulness of the NMIS signature and imaging system for arms control and nonproliferation
purposes has been recognized by NA-241. Other organizations have also expressed interest for the
NMIS system to provide a higher level of assurance that items in containers are consistent with the
declaration. NA-241’s primary interest is the use of NMIS imaging and signature capabilities for
possible treaty verification regimes. In addition, there are other organizations that have a strong
interest in NMIS capabilities for other applications. The user criteria for each of these applications
are different. An example of the image capability for highly shielded uranium is shown in Figures 2
and 3 below. In this case, an approximately six-inch diameter cylinder of depleted uranium (DU) is
shielded by four inches of lead on each side.
Figure 2. DU shielded by lead.
Figure 3. Image from shielded
DU cylinder scan.
2
Based on the interest in the use of NMIS for treaty regimes, funding was provided to move the
NMIS system in a direction from a fairly complicated, well-tested laboratory piece of equipment to
a more automated user friendly Fieldable NMIS (FNMIS) system that could be used in a treaty
regime application.
FIELDABLE NUCLEAR MATERIAL IDENTIFICATION SYSTEM (FNMIS)
FNMIS REQUIREMENTS FOR TREATY VERIFICATION PURPOSES
The first step in the design and fabrication process was obtaining a clear understanding of potential
treaty regime requirements. NA-241 and ORNL technologists and managers developed a design
criteria document over several months to ensure the equipment would be usable in a potential treaty
regime scenario. There are over 100 specific design criteria to ensure that these needs are met,
along with the needs of the technologists and designers. The following are some of the key criteria
addressed in the requirements document:













Imaging and signature capabilities
Assembly or disassembly within an hour
Assembly using two people
Modular design
Trained technicians with prior experience in nuclear field as operators
Imaging scans within specific time limits
Target rotation for multiangle tomographic images
Transportable by standard shipping and handling practices
Specified environmental and lighting conditions
Items measured within a specified volume
Target analyzed without moving the target (target rotation would not be allowed
in this mode)
Specific power use requirements
Authentication and information barrier needs considered during design
The entire list is too lengthy to be included in this paper in totality. This list is only intended to give
the reader an example of requirements criteria agreed to between the ORNL designers and the users.
It should also be noted that the requirements document is a living document that can be altered
when knowledge gained from the detailed design process and fabrication steps is implemented.
These changes require documented agreement between the designers and users. The system will
allow for future incorporation of a gamma ray spectrometry module.8
PRESENT FNMIS CONCEPT
The concept for the system is a FNMIS time-dependent coincidence system9,10 that incorporates
transmission tomographic imaging and utilizes a small, lightweight (30 lbs), portable D-T neutron
(14.1 MeV) generator (1 × 108 neutrons/second), proton recoil scintillation detectors, and a fast
(1GHz) time correlation processor. The system is being designed to allow for the eventual
incorporation of gamma ray spectrometry. The proton recoil scintillators are 32 small 2.5 x 2.5 x
10.2-cm thick plastic scintillators for imaging and two arrays of four 25 x 25 x 8-cm thick liquid
scintillators with online digital pulse shape discrimination to distinguish neutrons from gamma rays
or plastic scintillators. A computer-controlled scanner moves the small detectors and the source
3
appropriately for scanning a target object for imaging. The system is based on detection of
transmitted 14.1 MeV neutrons, fission neutrons, and gamma rays from spontaneous inherent source
fission of the target, fission neutrons, and gamma rays induced by the external D-T source, gamma
ray from natural emissions of uranium and Pu, and induced gamma-ray emission by the interaction
of the 14.1 MeV neutrons from the D-T source. This system is uniquely suited for detection of
shielded highly enriched uranium (HEU), plutonium, and other SNM. It will be adapted to utilize a
trusted processor that incorporates information barrier (IB) and authentication techniques using
open software and then be useful in some international applications for materials whose
characteristics may be classified. The proposed information barrier version of the FNMIS system
would consist of detectors and cables, the red (classified side) system that processes the data, and
the black (unclassified side) computer that handles the computer interface. The system could use
the “IB wrapper” concept proposed by Los Alamos National Laboratory (LANL) and the software
integrity (digital signatures) system proposed by Sandia National Laboratory (SNL). Since it is
based entirely on commercially available components, the entire system, including the FNMIS data
acquisition boards, can be built with commercial off-the-shelf components.
Figure 4. Top View Schematic of the FNMIS Equipment.
FNMIS CAPABILITIES
The system hardware and software can be configured to obtain the following: Pu presence, Pu mass,
Pu 240/239 ratio, Pu geometry, Pu metal vs. nonmetallic compound (absence of metal), U presence,
U mass, U enrichment, U geometry, and U metal vs. nonmetallic compound (absence of metal). A
matrix of the quantities determined (without the incorporation of gamma ray spectrometry), the
method of determination, whether active (external neutron source) or passive, and the measurement
equipment involved are given in Table 1. Some of these attributes can be obtained by multiple data
analysis methods. In addition, the imaging capability allows warhead authentication and
traceability of weapons parts and weapons components through dismantlement and can be used to
verify the destruction or change in form of SNM and other essential nonfissile components. In
addition, the data imaging measurements and MCNP-PoliMi (a Monte Carlo code for correlation
measurements) calculations of the FNMIS time correlation signatures can be used to obtain fissile
shape and mass without calibration. Very good initial estimates of the configuration of materials
from imaging can be provided for further refined Monte Carlo analyses. The system will be
modularly constructed with the RF (radio frequency) shielded modules connected to the processor
4
by appropriate control and signal cables in metal conduit. The system hardware and software
modules may also be configured to estimate a selected subset of these attributes. In addition,
signatures for fissile material can be used for template matching for confirmation of inventories and
receipts for weapons components. This was done in an operational mode at the Y-12 National
Security Complex in Oak Ridge for several years after 1996 where over 10,000 items were
measured.
This system has been designed to eventually incorporate gamma ray spectrometry. When included,
it will have the advantage of combining multiple technologies into a single system for a variety of
applications.
Table 1: Matrix of FNMIS Capabilities
Material
Active or
passive
1
time-dependent
coincidence
detect internal spontaneous
fission
active/passive
2
time-dependent
coincidence
measure density from neutron
transmission
active
3
time-dependent
coincidence
attenuation of gammas emitted
and multiplication depending on
density
active
geometry
1
time-dependent
coincidence
imaging
active
relative
Pu-content
1
time-dependent
coincidence
compare spontaneous and
induced fission rates
active
1
time-dependent
coincidence
measure induced fission rate
enhanced by imaging
active
2
time-dependent
coincidence
measure spontaneous fission rate
Passive
1
time-dependent
coincidence
transmission imaging
tomography
active
presence
metal/
nonmetal
Plutonium
Method
(option, implementation, basis)
Attribute
240
fissile mass
disposition or
conversion of
Measurement equipment
D-T neutron source (if active)
scintillation detectors
multichannel nanosecond time correlator
D-T neutron source
scintillation detectors
multichannel nanosecond time correlator
D-T neutron source
scintillation detectors
multichannel nanosecond time correlator
D-T neutron source
scintillation detectors
multichannel nanosecond time correlator
D-T neutron source
scintillation detectors
multichannel nanosecond time correlator
D-T neutron source
scintillation detectors
multichannel nanosecond time correlator
scintillation detectors
multichannel nanosecond time correlator
D-T neutron source
scintillation detectors
multichannel nanosecond time correlator
5
Table 1: Matrix of FNMIS Capabilities (continued)
Material
Method
(option, implementation, basis)
Attribute
time-dependent
coincidence
detect induced fission and
absence of internal spontaneous
fission
active
D-T neutron source
scintillation detectors
multichannel nanosecond time correlator
1
time-dependent
coincidence
measure density from neutron
transmission
active
D-T neutron source
scintillation detectors
multichannel nanosecond time correlator
2
time-dependent
coincidence
attenuation of gamma emitted
and multiplication depend on
density
active
D-T neutron source
scintillation detectors
multichannel nanosecond time correlator
geometry
1
time-dependent
coincidence
imaging
active
U235enrichment
1
time-dependent
coincidence
compare induced fission rates
and neutron transmission for
simple parts
active
fissile mass
1
time-dependent
coincidence
measure induced fission rate
complemented by imaging
active
disposition or
conversion of
1
time-dependent
coincidence
transmission imaging
tomography
active
spatial
distribution
1
time-dependent
coincidence
imaging plus D-T source pixel
correlated multiplicities
active
warhead
authentication
1
time dependent
coincidence
transmission imaging
tomography
active
traceability of
weapons/parts
1
time dependent
coincidence
transmission imaging
tomography
active
D-T neutron source
scintillation detectors
multichannel nanosecond time correlator
1
time dependent
coincidence
transmission imaging
tomography
active
D-T neutron source
scintillation detectors
multichannel nanosecond time correlator
1
time dependent
coincidence
transmission imaging
tomography
active
D-T neutron source
scintillation detectors
multichannel nanosecond time correlator
geometry
1
time dependent
coincidence
imaging
active
D-T neutron source
scintillation detectors
multichannel nanosecond time correlator
separation
from fissile
1
time dependent
coincidence
transmission imaging
tomography
active
D-T neutron source
scintillation detectors
multichannel nanosecond time correlator
Uranium
metal/
nonmetal
Dismantlement
High
explosive
Measurement equipment
1
presence
Fissile
Active or
passive
destruction of
nuclear
warhead
casings
destruction of
essential
nonnuclear
parts
D-T neutron source
scintillation detectors
multichannel nanosecond time correlator
D-T neutron source
scintillation detectors
multichannel nanosecond time correlator
High Purity Germanium (HPGe)
D-T neutron source
scintillation detectors
multichannel nanosecond time correlator
D-T neutron source
scintillation detectors
multichannel nanosecond time correlator
D-T neutron source
scintillation detectors
multichannel nanosecond time correlator
D-T neutron source
scintillation detectors
multichannel nanosecond time correlator
6
SUMMARY
ORNL and NA-241 have reviewed and agreed on the conceptual design and program planning
documents for the FNMIS. Funds have been provided, and the detailed design work for the
mechanical, software, and electrical portions of the FNMIS are well underway. The current
schedule for the completed system is lengthy. However, the system capabilities have been shared
with other organizations interested in supporting a fieldable system for their applications. It is
anticipated that with sufficient interest from other organizations and the additional interest in
establishing capabilities for potential treaty regimes, the length of time to complete the FNMIS will
be significantly reduced.
Upon completion, a well-planned neutron interrogation and imaging system will be available for:





treaty regime considerations;
mock treaty regime implementation testing;
experimental work to further advance NMIS capabilities;
material control and accountability use; and
SNM identification needs that arise around the nuclear complex.
In addition, a fully developed system can be evaluated by other organizations to determine their
respective needs. The coupling of these needs with the FNMIS design can ultimately produce
additional FNMIS systems at a lower cost and on a faster schedule due to the lessons learned during
the FNMIS design and fabrication.
The FNMIS will prove to be a very useful tool and will provide a high level of assurance that
declared items and materials are actually present.
7
REFERENCES
1. J. T. Mihalczo, J. A. Mullens, J. K. Mattingly, and T. E. Valentine, “Physical description of
nuclear materials identification system (NMIS) signatures,” Nuclear Instruments and Methods
in Physics Research, Section A, Volume 450, pp. 531–55, 2000.
2. J. T. Mihalczo, V. K. Paré, E. D. Blakeman, B. Damiano, T. E. Valentine, L. D. Phillips,
R. B. Bonner, D. B. Bopp, T. R. Chilcoat, J. DeClue, E. P. Elliott, G. D. Hackett, N. W. Hill,
D. J. Nypaver, L. H. Thacker, W. T. Thomas, J. A. Williams, and R. E. Zumstein, “NWIS
Signatures for Confirmatory Measurements with B33 Trainers,” Journal of Nuclear Materials
Management, Vol. 25, Issue 3, pp. 64–80 (June 1997).
3. J. A. Mullens, “Addition of Tomographic Capabilities to NMIS,” Y/LB-16,160, March 2003,
http://www1.y12.doe.gov/search/library/documents/pdf/ylb-16160.pdf.
4. Hausladen, P.A., et al. “Portable Fast-Neutron Radiography with the Nuclear Materials
Identification System for Fissile Material Transfers,” CAARI 2006:19th International
Conference on the Application of Accelerators in Research and Industry, Nuclear Instruments
and Methods in Physics Research Section B-Beam Interactions with Materials and Atoms,
Volume 261, Issue 1–2, pp. 387–390, August 2007.
5. J. A. Mullens, B. R. Grogan, D. A. Archer, and J. T. Mihalczo, “Shipping Anomaly from NMIS
Imaging,” Proceedings of 49th Annual Institute of Nuclear Materials Management Meeting,
Nashville, Tennessee (2008).
6. T. E. Valentine, J. T. Mihalczo, and J. A. Mullens, “NWIS Signatures For Identification of
Weapons Components at the Oak Ridge Y-12 Plant,” Proceedings of Institute of Nuclear
Materials Management Meeting, Phoenix, Arizona, July 20–24, 1997.
7. Wyatt, M. S., et al., 1998. “Characterization of an Enriched Uranyl Fluoride Deposit in a Valve
and Pipe Intersection Using Time-of-Flight Transmission Measurements with 252Cf,”
Proceedings of Institute of Nuclear Materials Management Meeting, Naples, FL,
July 26–30, 1998.
8. J. A. Mullens, P. A. Hausladen, D. E. Archer, M. C. Wright, and J. T. Mihalczo, “NMIS with
Imaging and Gamma Ray Spectrometry for PU, HEU, HE, Chemical Agents and Drugs,”
Oak Ridge National Laboratory, ORNL/TM-2006/76R1 (July 2007).
9. J. A. Mullens, J. E. Breeding, R. B. Perez, J. T. Mihalczo, T. E. Valentine, and J. A. McEvers,
“A Multipurpose Processor for Arms Control and Nonproliferation and NMC&A,” Proceedings
of Institute of Nuclear Materials Management Annual Meeting, July 1999.
10. J. T. Mihalczo, J. K. Mattingly, J. A. Mullens, J. A. McEvers, J. S, Neal, R. B. Oberer, and
J. D. White, “Oak Ridge Multiple Attribute System (ORMAS) for Pu, HEU, HE, Chemical
Agents, and Drugs,” ORNL/TM-2001/175 (2001).
8